Emulsion polymerization is an advantageous process involving radical chain polymerization of monomers in the form of colloidal dispersions. Emulsion polymerization bears some resemblance to suspension polymerization. Any similarities, however, are superficial as emulsion polymerization generally demonstrates significantly different reaction mechanisms and properties. Emulsion polymerization, for example, differs from suspension polymerization in the type and smaller size of the particles in which polymerization occurs, in the kind of initiator employed, and in the dependence of polymer molecular weight on reaction parameters. Emulsion polymerization additionally offers the unique advantage of being operable to simultaneously attain high molecular weights and high reaction rates.
Emulsion polymerization is used to manufacture several commercially important polymers. Fluorinated polymers and copolymers are examples of commercially important polymeric materials produced by emulsion polymerizations. Fluorinated polymers are used in various applications including the treatment of materials such as textiles, leather, carpet, and paper to impart hydrophobic and oleophobic properties to such materials. The polymerization of fluorinated monomers according to traditional emulsion polymerization techniques presents several challenges. One of the most difficult challenges is addressing the solubility variances between the hydrophobic fluorinated monomers and the aqueous dispersing medium. In order to increase the solubility of fluorinated monomers in the aqueous dispersing medium, water-soluble organic cosolvents are often added to the dispersing medium.
The addition of organic cosolvents to the dispersing medium, while enhancing solubilization and polymerization of hydrophobic species, presents several drawbacks. Many of the organic cosolvents used in emulsion polymerization processes, for example, are accompanied by governmental regulations due to various environmental considerations, which can increase costs to ensure compliance with the regulations. Moreover, organic cosolvents can negatively impact various properties of polymeric dispersions. Organic cosolvents, for example, can negatively impact the desired repellant and protective properties of the polymeric dispersion, especially when the polymeric dispersion is applied to a substrate such as a fabric. Additionally, organic cosolvents can negatively impact wash fastness and other fastness of dispersed dyed textile substrates that have been treated with polymeric dispersions comprising organic cosolvents.
Organic cosolvents can be distilled out of polymeric dispersions. The distillation process, nevertheless, increases production time and the energy required to produce the polymeric dispersions. Distillation procedures can additionally destabilize the polymeric dispersion. Furthermore, many organic cosolvents suitable for use in emulsion polymerization systems are costly adding even more expense to the production process.